1. Field of the Invention
The present invention relates to a system and a method for the detection of defects or damages of a coating and, more particularly, to a system and a method for the detection of defects or damages of a coating, which involves mounting an object to be investigated onto a carrier, fetching an image of the object through an investigating robot while transferring the carrier with the object mounted thereon, and detecting such defects or damages of a coating formed on the surface of the object by processing the image of the object with an image processing means.
2. Description of the Related Art
For example, a line for the preparation or assembly of automotive vehicles has a wet rubbing sub-line for rubbing the vehicle bodies in a wet state disposed at the side downstream of a sub-line for coating the vehicle bodies with an intermediate coating paint. The wet rubbing sub-line is provided with a vehicle models detecting station at its upstream side, a coat defects detecting station at its intermediate side, and a repair station at its downstream side. The vehicle bodies are transferred at a given speed over the entire length through various stations while held with or loaded on a chain conveyor.
In the coat defects detecting station, the vehicle bodies are subject to investigation as to whether defects or damages are caused on the coating formed on their surfaces. The coat defects detecting station has an investigating robot disposed, which in turn is provided with an image pickup unit so arranged as to take an image of the surface of the coating formed on the vehicle body as an object to be investigated, for example, while transferring the investigating robot at a given speed in the direction opposite to the direction of movement of the vehicle body. An image of plural regions of the vehicle body is taken at different locations of the investigating robot.
The images taken are subjected to processing with an image processor and, when any defects or damages are to be detected on the coating formed on the vehicle body, such defects or damages are repaired in the repair station disposed on the side downstream of the coat defects detecting station. The defects or damages can be repaired with a rubbing tool mounted on the investigating robot.
For example, Japanese Patent Unexamined Publication No. 62-233,710 discloses an image pick-up unit so adapted as to take images of plural regions. This image pick-up unit can detect defects or damages of the surface of an object to be investigated, such as a coating on a vehicle body panel by radiating a laser slit light onto the surface of the coating thereon.
On the other hand, it is considered that defects or damages caused on the surface of a coating formed on the object be detected by allowing an investigating robot to fetch an image of the object while the object loaded on a carrier is transferred together with the carrier and then by subjecting the image thereof to image processing with an image processing means.
When the carrier is transferred with a conveyor or such similar device, the surging may be caused to occur due to changes of a load or due to start-up or suspension of the carrier or for other reasons. Further, a deviation may be caused between the actual position of the carrier and its position detected due to a free space between the conveyor and the carrier loaded thereon. These matters may make an actual image fetch width different in size, not constant, leading to the risk of missing investigation.